Nifedipine is the generic name for 4-(2'-nitrophenyl)-2, 6-dimethyl-3, 5-dicarbomethoxy-1, 4-dihydropyridine, an important vasodilator. It is light-sensitive and practically insoluble in water, so the preparation of formulations has been the subject of numerous Patent Specifications. Most have been concerned to achieve a rapid release of nifedipine into the blood stream. However, EP 47899 describes compositions containing crystals of particularly large surface area, which can be made into small tablets and give a long effective period but the preparation of such crystals is laborious. U.S. Pat. No. 4880623 describes sustained release compositions prepared by a lengthy, involved process productive of weighty tablets. Nomidipine is a similar medicine.